In machines which have a cyclic operation wherein, during each cycle, one or more operations are to be performed, it has been customary in the past to control the timing of these operations within a cycle by various means. For example, a rotating shaft may have cams thereon, each of which actuates a switch at a predetermined point or degree in the machine cycle, which causes a certain operation to be performed. When it is desired to change the degree in the machine cycle at which a particular operation occurs, however, it becomes necessary to change the cam associated with that operation, or provide cams which are adjustable. This may be time consuming and troublesome and usually requires that the machine be shut down while being adjusted. This usually is a repetitive trial and error procedure until the required adjustment is made. Furthermore, being mechanical devices, the cams and switches require maintenance.
Another method of controlling the timing of operations within a machine cycle has been to count pulses emitted by a pulse generator so that an operation associated therewith may be caused to occur at the time a predetermined number of pulses have been counted in each machine cycle. Such a system, however, has the disadvantage of being more expensive and of being more difficult to change the setting, since it requires reset of the memory to a different count.
The present invention is designed to provide electronic control means for cyclically operating machines which overcome the disadvantages of controls heretofore known, as well as to simplify the operation of such controls and make them less expensive. Also, this invention permits fine adjustment of the degrees in the machine cycle at which the operations are to occur for optimum performance while the machine is cycling.